LCDs of the internal/external dual lighting type which are employed in cell phones and the like include a liquid-crystal display module unit and a backlight unit which are fixed to each other with a pressure-sensitive adhesive tape as shown in FIG. 7 (see JP-A-2002-249741, JP-A-2002-23663, and JP-A-2002-235053). (The term “JP-A” as used herein means an “unexamined published Japanese patent application”.) This pressure-sensitive adhesive tape is required to have the property of reflecting light and the property of shutting off light having specific wavelengths. Light-reflecting properties are necessary for reflecting the light from the backlight to thereby enhance luminance and reduce the power consumption based on the effective utilization of reflected light. On the other hand, light-shutting properties are necessary for inhibiting the light from the backlight from leaking out to the LCD surface to cause viewing failures.
Pressure-sensitive adhesive tapes which reconcile light-reflecting properties and light-shutting properties have hitherto been investigated. Pressure-sensitive adhesive tapes of this kind generally have a colored layer disposed on one side of the substrate film or have a colored pressure-sensitive adhesive layer. In general, a white layer is disposed on the backlight side in order to reflect the light from the backlight, and a black layer is disposed on the liquid-crystal display module side in order to prevent the light from leaking out to the LCD surface. For example, a pressure-sensitive adhesive tape employing a substrate film colored white has a transparent pressure-sensitive adhesive layer disposed on the backlight side and has a black layer or black-pressure-sensitive adhesive layer disposed on the liquid-crystal display module side. A pressure-sensitive adhesive tape employing a substrate film colored black has a white layer or white pressure-sensitive adhesive layer disposed on the backlight side and has a transparent pressure-sensitive adhesive layer on the liquid-crystal display module side. Furthermore, a pressure-sensitive adhesive tape employing a transparent substrate film has a white layer or white pressure-sensitive adhesive layer disposed on the backlight side and has a black layer or black pressure-sensitive adhesive layer disposed on the liquid-crystal display module side.
However, in order to reconcile light-reflecting properties and light-shutting properties with such a pressure-sensitive adhesive tape, it is necessary to superpose many colored layers or to form colored layers thickly. This has resulted in a problem that the pressure-sensitive adhesive tape comes to have an increased total thickness and be unable to conform to thickness and weight reduction in cell phones and the like.